Air conditioners are sized in kilowatts (kW) of cooling. Get it right and the room stays comfortable all summer while the unit purrs along quietly. Get it wrong and you either struggle on hot days or pay for a unit that keeps switching on and off.
A quick guide
- 2.0 kW: small and medium bedrooms and home offices, up to around 16–18 m².
- 2.5 kW: larger bedrooms and small living rooms, up to around 22 m².
- 3.5 kW: living rooms and kitchen-diners, up to around 30 m².
- 5.0 kW and above: large open-plan spaces, conservatories and garden rooms.
What else matters
Sun makes the biggest difference: a south-facing room with big windows can need 15–20% more capacity than the same room facing north. Conservatories and loft rooms need much more per square metre. Kitchens carry extra heat from cooking. High ceilings add volume.
Why bigger isn't better
An oversized unit cools the air quickly then switches off before it has removed the humidity, so the room feels cold and clammy. It also costs more to buy. The right size runs steadily at low power, which is quieter, more comfortable and cheaper to run.
Our estimator sizes each room for you, and we confirm it properly at the free survey. Try the estimator or book a free survey.